Bob Vander Plaats, president of The Family Leader (right) speaks before a bus tour to urge Iowans to vote state Supreme Court Justice David Wiggins off the bench, in Des Moines, Iowa, on Monday.

Charlie NeibergallAP

A battle is under way in Iowa over whether a state Supreme Court justice can keep his job.

Critics have launched an all-out campaign to throw him off the bench because of his ruling three years ago clearing the way for same-sex marriage. The judge's supporters are fighting back, but they may need to get over their reluctance to mix politics and the judiciary.

Christian conservatives are still energized by their victory in 2010, when they voted down three justices for their same-sex marriage ruling. Judges in Iowa are appointed, not elected, but they face periodic retention votes to keep their jobs.

This year, Justice David Wiggins is on the ballot. And the conservatives are taking their "No Wiggins" campaign on a bus tour this week. Former GOP presidential candidate Rick Santorum spoke at the start of the tour on Monday. Boarding the bus near the state capital, evangelical leader Bob Vander Plaats rallied for a repeat of the 2010 vote.

"It was over half a million Iowans who voted 'no' to hold those justices accountable. So now we're in this campaign again to say, 'We have to vote no on Wiggins,' " said Vander Plaats.

Following along the same route is another bus tour, dubbed, "Yes to Iowa Judges." It's part of a campaign to keep Wiggins on the bench. But overall, the pro-Wiggins camp is striking a different tone with the slogan: "Vote Justice, Not Politics."

The group known as Justice Not Politics is holding educational forums like a recent one in Iowa City. But it's not a rally — it's more a seminar on how the retention vote is supposed to work.

That is — it's not meant to punish particular Supreme Court rulings.

Linda McGuire, with the University of Iowa law school, says the same-sex marriage ruling was unpopular, but she says that's part of an independent judiciary.

"There's a real populist movement happening to try to attack the judicial system as, quote, 'out of touch with the popular sentiment of the people.' And that's just a basic misunderstanding of what courts are about," McGuire says.

Justice Not Politics legally can raise money and urge a "yes" vote. But they're reluctant to say, specifically, "Vote yes for Wiggins." And they won't run ads.

Wiggins himself wrote an op-ed in the Des Moines Register this month saying politics should stay out of Iowa courts. One judge who was ousted in 2010 fears that won't work.

"I hope I'm wrong," says former Iowa Supreme Court Justice Michael Streit. He says he and his fellow justices made a conscious decision not to campaign for their own retention two years ago.

But now?

"If these forces keep picking off justices and are successful, I don't know how you, you either let them destroy our court system or you have to fight back," says Streit.

Justices are also being targeted in Florida after they issued an unpopular health care ruling. Rebecca Kourlis, with the University of Denver's Institute for the Advancement of the American Legal System, says it's opened up a whole new debate over how states select judges.

"It gives fuel to the fire, that, well, maybe we should just try to figure out a way to get a federal system in place at the state level with lifetime appointments and Senate confirmation," Kourlis says.

Meanwhile, back in Iowa as the dueling bus tours continue, the two sides have one message in common: In the voting booth, turn the ballot over. The justice retention question is on the back. Last time, a lot of voters missed it.

Now to a political battle in Iowa over a state Supreme Court justice. Critics have launched an all-out campaign to throw him off the bench because of his vote in a unanimous ruling that cleared the way for same-sex marriage in Iowa. The judge's supporters are fighting back. But as we hear from Joyce Russell of Iowa Public Radio, they may need to get over their reluctance to mix politics and the judiciary.

JOYCE RUSSELL, BYLINE: Christian conservatives are still energized by their victory in 2010 when they voted down three justices for their same-sex marriage ruling. Judges in Iowa are appointed, not elected, but they face periodic retention votes to keep their jobs. This year, Justice David Wiggins is on the ballot, and the conservatives are taking their No Wiggins campaign on a bus tour this week. Boarding the bus near the state capitol in Des Moines, evangelical leader Bob Vander Plaats rallies for a repeat of the 2010 vote.

BOB VANDER PLAATS: It was over half a million Iowans who voted no to hold those justices accountable. So now we're in this campaign again to say we have to vote no on Wiggins.

RUSSELL: Following along the same route is another bus tour dubbed Yes to Iowa Judges. It's part of the campaign to keep Wiggins on the bench. But overall, the pro-Wiggins camp is striking a different tone.

UNIDENTIFIED WOMAN #1: Vote justice, not politics.

UNIDENTIFIED WOMAN #2: Yes, thanks for coming. This is such an important issue.

RUSSELL: The group known as Justice Not Politics is holding forums like this one in Iowa City, but it's not a rally. It's more a seminar on how the retention vote is supposed to work, that is, it's not meant to punish particular rulings. Linda McGuire with the University of Iowa Law School says the same-sex marriage ruling was unpopular, but she explains that's part of an independent judiciary.

LINDA MCGUIRE: There's a real populist movement happening to try to attack the judicial system as, quote, "out of touch" with the popular sentiment of the people. And that's just a basic misunderstanding of what courts are about.

RUSSELL: Justice Not Politics legally can raise money and urge a yes vote, but they're reluctant to say specifically vote yes for Wiggins, and they won't run ads. One ousted justice fears that won't work.

MICHAEL STREIT: I hope I'm wrong.

RUSSELL: That's former Iowa Supreme Court Justice Michael Streit. He says he and his fellow justices made a conscious decision not to campaign for their own retention two years ago. But now?

STREIT: If these forces keep picking off justices and are successful, I don't know how you - you either let them destroy our court system or you have to fight back.

RUSSELL: Justices are also being targeted in Florida after they issued an unpopular health care ruling. Rebecca Kourlis is with the University of Denver's Institute for the Advancement of the American Legal System. She says it's opened up a whole new debate over how states select judges.

REBECCA KOURLIS: It gives fuel to the fire that, well, maybe we should just try to figure out a way to get a federal system in place at the state level with lifetime appointments and Senate confirmation.

RUSSELL: Meanwhile, back in Iowa, as the dueling bus tours continue, the two sides have one message in common: in the voting booth, turn the ballot over. The justice retention question is on the back. Last time, a lot of voters missed it. For NPR News, I'm Joyce Russell in Des Moines. Transcript provided by NPR, Copyright NPR.